Bash function to add a hostname:ip entry into your /etc/hosts file

update_etc_hosts.sh

#!/bin/bash
# Usage:
# update_etc_hosts "some-host-name" "some-ip-addr"
update_etc_hosts () {
  HOST_NAME=$1
  HOST_IP=$2
  NO_SUDO=$3
  HOST_ENTRY="$HOST_IP $HOST_NAME"
  HOSTS_FILE="/etc/hosts"
  TMPFILE=$(mktemp)
  echo "Adding '$HOST_IP $HOST_NAME' entry to '$HOSTS_FILE'"
  if grep -q "^[^#]*$HOST_NAME" "$HOSTS_FILE" ; then
    echo "Replacing existing '$HOST_NAME' entry."
    awk "!/^[^#].*$HOST_NAME/ {print \$0}" "$HOSTS_FILE" > "$TMPFILE"
  else
    cp $HOSTS_FILE $TMPFILE
  fi
  echo -e "$HOST_ENTRY" >> "$TMPFILE"

  if [[ $NO_SUDO = "NO_SUDO" ]]; then
    cat "$TMPFILE" > "$HOSTS_FILE"
  else
    echo "Modifying $HOSTS_FILE requires sudo privileges, please enter your password."
    sudo -k sh -c "cat \"$TMPFILE\" > \"$HOSTS_FILE\""
  fi
  rm "$TMPFILE"
}